The present invention relates to computer animation. More particularly, the present invention relates to spreading the brightness of a set of light sources at a surface to generate a specular reflection and a fuzzy reflection that is adjacent to the specular reflection.
Throughout the years, movie makers have often tried to tell stories involving make-believe creatures, far away places, and fantastic things. To do so, they have often relied on animation techniques to bring the make-believe to “life.” Two of the major paths in animation have traditionally included, drawing-based animation techniques and stop motion animation techniques.
Drawing-based animation techniques were refined in the twentieth century, by movie makers such as Walt Disney and used in movies such as “Snow White and the Seven Dwarfs” (1937) and “Fantasia” (1940). This animation technique typically required artists to hand-draw (or paint) animated images onto transparent media or cels. After painting, each cel would then be captured or recorded onto film as one or more frames in a movie.
Stop motion-based animation techniques typically required the construction of miniature sets, props, and characters. The filmmakers would construct the sets, add props, and position the miniature characters in a pose. After the animator was happy with how everything was arranged, one or more frames of film would be taken of that specific arrangement. Stop motion animation techniques were developed by movie makers such as Willis O'Brien for movies such as “King Kong” (1933). Subsequently, these techniques were refined by animators such as Ray Harryhausen for movies including “Mighty Joe Young” (1948) and Clash Of The Titans (1981).
With the wide-spread availability of computers in the later part of the twentieth century, animators began to rely upon computers to assist in the animation process. This included using computers to facilitate drawing-based animation, for example, by painting images, by generating in-between images (“tweening”), and the like. This also included using computers to augment stop motion animation techniques. For example, physical models could be represented by virtual models in computer memory, and manipulated.
One of the pioneering companies in the computer-aided animation (CA) industry was Pixar. Pixar is more widely known as Pixar Animation Studios, the creators of animated features such as “Toy Story” (1995) and “Toy Story 2” (1999), “A Bugs Life” (1998), “Monsters, Inc.” (2001), “Finding Nemo” (2003), “The Incredibles” (2004), “Cars” (2006) and others. In addition to creating animated features, Pixar developed computing platforms specially designed for CA, and CA software now known as RenderMan®. RenderMan® was particularly well received in the animation industry and recognized with two Academy Awards®. The RenderMan® software included a “rendering engine” that “rendered” or converted geometric and/or mathematical descriptions of objects into a two dimensional image. The named inventor of the present invention co-developed the original RenderMan® software.
Reducing rendering time is very important for computer animation. The rendering process can be a time consuming operation that may take hours, if not days, when rendering a scene with many objects. As an example, if a scene included ten thousand light sources, the rendering engine might have made ten thousand squared calculations to render a pixel in a scene. Accordingly, the time to render such a scene would be unacceptably long. Multiplying this rendering time by the number of frames (e.g. 130,000) in a typical feature-length animated feature of images results in a rendering time that is impractical.
Various rendering techniques have been used to accelerate rendering of images for matte (or non-specular) surface wherein the light sources were modeled as being infinitely distant. Such techniques include image mapping techniques, wherein an image map is generated and surrounds a point at an origin for which an image is rendered. Such techniques fail to take into account far-field and mid-field lighting effects that are not necessarily associated with an infinite light source. Moreover, such techniques fail to provide for specular reflections and the effects associated therewith, such as the glow (or fuzziness) that surrounds a central position of a specular reflection.
Therefore, new methods and apparatus are needed for approximating light sources and/or objects illuminated by the lights such that these methods and apparatus may be used to substantially realistically render the objects in animated scenes.